多重手征双重带中的八极关联研究

After the prediction of chiral doublet bands in 1997 and their first observation in 2001, up to now about 40 candidate chiral nuclei have been reported. Based on the covariant density functional theory the new phenomenon called multiple chiral doublets (MχD) has further been predicted in 2006 and its first example of MχD has been first observed in the nucleus 133Ce in 2013. Since then, the study of nuclear chirality has been shifted gradually to focus on the exploration of MχD. And in 2016, the first experimental evidence of the simultaneous spontaneous breaking of chiral symmetry and space reflection symmetry has been found in 78Br, which has prompted us to carry out the present project of "Octupole correlations in multiple chiral doublet bands". The main contents include: 1) to develop the reflection asymmetric triaxial particle rotor model; 2) to describe the observed multiple chiral bands with octupole correlations in nuclei; 3) to carry out the model investigation of chiral parity quartet bands; 4) to improve the single particle potential in the model for promote the model predictive ability; 5) to explore the chiral parity quartet bands with the close collaboration with experimentalists. It is expected to develop a phenomenological particle rotor model which can be used to describe the multiple chiral bands with octupole correlations and the chiral parity quartet bands, and combining with the experimental work, to shed some new light on the understanding of nuclear chirality.

自1997年理论预言原子核手征性并于2001年被实验证实以来，迄今实验上已报道四十例左右的手性原子核。2006年基于协变密度泛函理论预言的多重手征带新现象，于2013年在133Ce中首次得到证实。由此，手征性研究的重心已经逐渐转移到多重手征带的探索之上。而2016年，首次在78Br中发现了手征对称性和空间反射对称性联立自发破缺的实验证据，促使我们开展“原子核多重手征双重带的八极关联研究”这一课题。项目内容主要包括：1）发展反射不对称的三轴粒子转子模型；2) 描述实际原子核中的八极关联的多重手征带；3）开展手征宇称四重带的模型研究；4）改进模型中的单粒子势，提升模型的预言能力；5）理论密切联系实验，相互促进，探索手征宇称四重带。通过该课题的研究，将得到研究原子核八极关联的多重手征带和手征宇称四重带的唯象粒子转子模型方法，并将与实验工作紧密结合，拓宽人们对原子核手征性的认识和了解。

原子核的手征性是核物理研究的前沿领域。2016年，人们首次发现了手征对称性和空间反射对称性联立自发破缺的实验证据，促使我们开展“原子核多重手征双重带的八极关联研究”这一课题。项目围绕着原子核的手征对称性和空间反射不对称性，重点聚焦于多重手征双重带的八极关联与两种对称性的联立自发破缺，进行了多方面的研究和探索。主要研究成果包括：建立反射不对称的三轴粒子转子模型，研究78Br中的八极关联的多重手征双带；构建描述手征宇称联立破缺体系的反射不对称三轴粒子转子模型，提出“手称”和“手宇称”的新概念, 给出了相应的电磁跃迁选择定则和实验信号；利用反射不对称三轴粒子转子模型研究了手性原子核124Cs，预言其中八极关联的多重手征双带现象；利用建立的反射不对称三轴粒子转子模型研究了73Br中的正负宇称带，解释了其带间增强的E1跃迁几率；在核芯粒子耦合模式下，并假定核芯具有类似T(5)的临界对称性，研究了奇奇核的临界点对称性，预言过渡区的奇奇核存在集体的多重手征双带等。